When registering for an account here, a new user must agree to the forum rules. Among other things, a user must warrant that they will not post any messages that are sexually-oriented. But as far as I can tell, the forum rules do not include a ban on sexually-oriented posts, and it seems like sexually-oriented posts are fairly common here. Assuming that sexually-oriented posts are in fact allowed here, I would suggest that the rules text on the registration page be edited to reflect this.